Signaling system



April 18, 1939.

J.V C. WALTER SIGNALING SYSTEM AFiled oct. 3, 1956 3 Sheets-Sheet lApril 18, 1939.` J. c. WALTER i SIGNALING SYSTEM Filed Oct. 3, 1936 3Sheets-Sheet 2 IN V EN TOR.

ATTORNEY April 18, 1939.` J. C; WALTER 2,154,923

SIGNALING SYSTEM Filed Oct. 5, 1956-- 3 Sheets-Sheet 5 lil-:1.13-5

TRANSMITTER RECEIVER RECEIVER AREA AREA COVERED BY COVERED BY f=555onos. Ef=173nu KCS.

17300 KCS' HEAvlSmE (Ef) REFLECTING 355m KCS. /Y n LAYER TRANSMITTER RRECElVER Q EARTH 77 IN V EN TOR. on C wolf/bev A TTORNEY.

Patented Apr. 18, 1939 UNITED STATES PATENT OFFICE SIGNALIN G SYSTEMration of Delaware Application October 3,

2 Claims.

This invention pertains in general to signaling systems, andspecifically relates to a multiple signaling system.

The present invention deals with the transmission of programs to severalremote points. For example, it may be desired to transmit one or moreprograms to several distribution points, such as wired radio networkslocated in cities remotely situated from each other. When it is desiredto transmit a signal to two such distant points by high frequency waves,the selection of the most effective frequency for each leg of thecircuit must be made with respect to conditions controlled by theKenelly-Heaviside effect. If the receiving points are considerablydisplaced from one another and from the transmitter, the selection of aneflicient frequency for simultaneous transmission to both receivingpoints becomes difcult and reaches the point of impossibility when thedistances become remote from each other, as, for example, when thepoints of reception for daylight transmission are located approximately1000 miles and 3000 miles from the transmission point. With respect tothese particular distances, it has been found that 8650 kilocycles isthe most reliable frequency for the 1000 mile transmission length, whilea frequency in the neighborhood of 17,000 to 18,000 kilocycles is mosteective for the 3000 mile transmission length. While using the 8650kilocycles on the 1000 mile length, it is found that the signal is heardWith marked intensity at points from 400 to 1200 miles from thetransmitter, but beyond 1200 miles severe attenuation sets in. At the3000 mile point, the signal is practically nonexistent. Althoughspecific distances are used by way of illustration, similar conditionsprevail for other correlated conditions.

A frequency of 17,300 kilocycles appears to be efficient fortransmission to a reception point between 1800 and Li000 miles. However,the skip effect for this frequency makes it uneifective for transmissionto the receiving point located 1000 miles from the point oftransmission. The use of intermediate frequencies is also fraught withdifficulty due to severe fading resulting from only slight changes inthe Kenelly- Heaviside layer.

rlhe principal object of the present invention consists in providing amultiple transmission system for transmitting programs to pluralreception points substantially displaced from one another.

A further object of the invention comprises providing a transmissionsystem for simultane- 1936, Serial No. 103,921

(Cl. Z50-6) ously transmitting a program to a plurality of remote pointsby commonly developed frequencies of different orders.

A further object of the invention consists in the method of transmittingwith respect to the 5 Kenelly-Heaviside layer for simultaneouslypropagating waves by reflection from a common transmission point to aplurality of remotely situated receiving points.

These and other objects are accomplished by 10 the following, referencebeing had to the accompanying drawings in which like reference numeralsdesignate corresponding parts and in which:

Fig. l is a schematic representation of a pre- 15 ferred system ofpropagation in accordance with the principles of the invention;

Fig. 2 is a diagrammatic representation of circuits employed in thesystem of Fig. 1; 20

Fig. 3 is a graphical representation of transmission conditions inaccordance with the invention; and

Fig. 4 is another graphical representation of transmission conditions inaccordance with the invention. 25

Referring to the drawings in detail, and particularly to Fig. l, aprogram source l is connected with a common transmission unit 2 whichcontrols the transmitter 3, designated as transmission unit A, and atransmitter 5, designated as transmission unit B. The program source Icomprises one or more studios and audio amplication equipment forproducing one or more channels of audio frequency program modulationenergy. The program energy from source I is conveyed to the commontransmission unit 2.

The common transmission unit 2 is connected with a master oscillator 2afor producing a base frequency and a harmonic generator 2b to develop afundamental high frequency f from which is derived a second harmonicfrequency 2f, both modulated by the program energy to produce carrierand side band modulation frequencies. The master oscillator basefrequency 2q may be of any conventional type of crystal controlledelectron tube oscillator, and the harmonic generator 2b may be of aconventional type for producing harmonics. Reference is made to UnitedStates Patents Nos. 1,912,322 and 1,766,047. When it is desired totransmit more than one program, the several programs can be individuallyutilized to modulate intermediate carrier frequencies, which carrierfrequencies are utilized to modulate the frequencies f and 2f and appearin connection therewith as modulation ll-x side bands. The carrierfrequencies f and 2f are conveyed to the transmitter units 3 and 4 whichrespectively comprise power'ampliers and associated circuits fortransmitting the respective frequencies.

Fig. 2 illustrates, in more detail, part of the circuits utilized in thetransmitting units shown in Fig. 1. Referring to Fig. 2, the commontransmission unit 2 includes a push-pull amplifier having electron tubesI5 and I6 operating through a tuned circuit including inductance I'l andcapacitor I8. Capacitive couplings are provided from the unit 2 to theunit 3 and to the unit 4.

The unit 3 includes an input tuned circuit comprising inductance I9 andcapacitor 20 serving to energize the input electrodes of poweramplifying electron tubes 2I and 22. The anode or output circuit oftubes 2| and 22 includes an output resonance circuit having theinductance 23 and capacitor 24. The inductance 23 is coupled withinductances 26 and 21 which operate through capacitors 28 and 29 toenergize an antenna system including the array 30 and ground 3I. Theantenna system S0-3l, in conjunction with the unit 3, as energized byunit 2, transmits the modulated carrier frequency f. Circuit componentsnot shown in the unit 3 of Fig. 2 are of conventional form.

Unit 4 comprises circuit components corresponding with related parts ofthe unit 3 with the exception that the parameters of these circuitcomponents are adjusted so that the circuit as a whole, in cooperationwith antenna system 3Ilb-3Ib, transmits the modulated carrier energy atfrequency 2f. For purposes of illustration, the frequencies f and 2f maybe 8650 kilocycles and 17,300 kilocycles, respectively.

Referring again to Fig. l, the waves propagated from the antenna systemof unit 3 are received by equipment 5, designated as receiver A.Equipment 5 receives the high frequency short wave signals from unit 3and converts such signals into modulation energy suitable forcontrolling a local transmitter 6. The local transmitter 6 comprises alocal master oscillator for producing a base frequency which may have anharmonic relationship with, and be controlled by, the frequency of themaster oscillator of unit 2. This may be accomplished by a wire lineconnecting the latter oscillator with the local oscillator. Such wireline need not be of the high quality required to transmit a band offrequencies, inasmuch as it is required to transmit the base frequencyonly. It is preferable, however, in View of the long distance betweenthe several transmitters to use a component of the space radio fromreceivers A and B to control respectively the frequencies of the localmaster oscillators. This may be accomplished in a known manner byfrequency dividers. The purpose of this controlled or synchronizedrelationship is to insure that all of the transmission frequencies usedin the system are kept directly or harmonically in step. The transmitter6 also includes means in the form of a sub-harmonic polyphase generatorfor developing polyphase carrier frequency within a frequency rangesuitable for impression on a power transmission network such as withinthe range of 26-78 kilocycles. The master oscillator and harmonicpolyphase generator may be of conventional form for producing theresults desired. Preferably, the master oscillator is of a crystalcontrolled, electron tube type with the crystal ground to the samefrequency as the frequency of the oscillator 2a, or a harmonic thereof.Reference is made to United States Patents Nos. 1,622,135; 1,730,412;1,820,898 and 1,823,851. The program modulation energy is utilized tomodulate such carrier frequency energy which is then placed upon thetransmission medium I designated as transmission network A. Thetransmission network A comprises a power network such as the commercialalternating current distribution system of a municipality and includespower generators, voltage control equipment, and distribution lines tothe consumers circuits which include both power and wired radioreceiving equipment.

Equipment 5B, designated as receiver B, corresponds to equipment 5,designated as receiver A, except that the receiver B is adjusted forreception of frequency 2f after being transmitted from equipment 4,designated as transmission unit B.

The receiver B operates to receive the program energy transmitted fromunit 4, as represented by the high frequency short wave signalscomprising frequency 2. This received energy is converted into themodulation energy which controls the equipment 6B and equipment 'IBwhich correspond in nature and function with equipments t and 7,respectively, except that the two systems connected respectively withreceiver A and receiver B are geographically displaced to a considerableextent. For example, the receiver A may be situated 1000 miles from thetransmission point, and receiver B may be situated 3000 miles from thetransmission point.

Fig. 3 illustrates the effective transmission eld areas in whichreceiver A and receiver B are located with respect to the transmitter.Fig. 4 illustrates the reiected propagation of waves to receivers A andB by virtue of the different frequencies. is reflected by theKenelly-Heaviside layer to the receiver A, and that the frequency 2 ,fis reflected by the Kenelly-Heaviside layer to the receiver B, therebypermitting both receivers to receive the same program by frequenciesharmonically related to each other and to a base frequency.

Although a specific embodiment of the system has been disclosed, it willbe obvious that many changes and modifications can be made withoutdeparting from the intended scope of the inu vention. Therefore, nolimitations are intended except as pointed out in the appended claims.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

l. A signaling system comprising, a source of program modulation energy,a transmission source associated with said program source for producingfrom a base frequency and transmitting through space a plurality ofdifferent carrier frequencies all harmonically related to each other andto said base frequency and all modulated by said program modulationenergy, receiving stations positioned at points geographically displacedwith respect to said transmission source, said receivers beingindividually responsive only to a particular one of said carrierfrequencies, a retransmission System connected with each of saidreceivers, said retransmission systems each including means forgenerating a local master frequency and deriving therefrom asub-harmonically related retransmission frequency, said local masterfrequency being harmonically related to said base frequency, meansincluding the output of said receivers for modulating said harmonicallyrelated retransmission It will be seen that the frequency f frequencies,and means for transmitting the frequencies thus modulated.

2. A signaling system comprising, a source of program modulation energy,a transmission source associated with said program source for producingfrom a base frequency and transmitting through space a plurality ofdifferent carrier frequencies all harmonically related to each other andto said base frequency and all modulated by said program modulationenergy, receiving stations positioned at points geographically displacedwith respect to said transmission source, said receivers beingindividually responsive only to a particular one of said carrier fre- 15quencies, a retransmission system connected with each of said receivers,said retransmission systems each including means fo-r generating a localmaster frequency and deriving therefrom a sub-harmonically relatedretransmission frequency, said local master frequency being harmonicallyrelated to said base frequency, a Wired radio network including a powerdistribution system connected with each of said retransmission systems,means including the output of said receivers for modulating saidharmonically related retransmission frequencies, and means fortransmitting the frequencies thus modulated over said Wired radionetworks.

JOHN C. WALTER.

